1. Field of the Invention
The present invention relates to an endoscope insertion portion of an endoscope having a plurality of observation optical systems.
2. Description of the Related Art
Conventionally, endoscopes have been widely used in the medical field and the like. With an endoscope, for example, internal organs in a body cavity can be observed by inserting an elongated insertion portion into the body cavity, and various treatments can be performed using a treatment instrument inserted into a treatment instrument insertion channel as necessary. At a distal end of the insertion portion, a bending portion is provided. By operating an operation portion of the endoscope, observing direction of an observation window at a distal end portion can be changed.
In general, an endoscope is provided with an air/water feeding nozzle for cleaning for a case where body fluid or the like adheres on an outer surface of the objective optical system of the endoscope to disturb the observation when the endoscope is inserted into the body cavity. The outer surface of the objective optical system of the endoscope can be secured of a clean observation field of view with, for example, a cleaning liquid spouted out or air sprayed from the air/water feeding nozzle.
For example, an endoscope having a plurality of objective optical systems is proposed as described in Japanese Unexamined Patent Application Publication No. 06-154155. This endoscope has a plurality of image pickup units, wherein the plurality of objective optical systems and an aperture of an air/water feeding nozzle are located at a distal end of an insertion portion to line up on a generally straight line.
Also, an endoscope used in recent years has a duct (hereinafter referred to as a treatment instrument channel) through which various forceps are inserted or body fluid, filth in a body cavity, and the like, are sucked, and a duct (hereinafter referred to as a forward water-feeding channel) from which a cleaning liquid is spouted in a direction of a diseased part for cleaning a mucous membrane and the like adhered on the diseased part as a region to be inspected. Respective aperture portions of these treatment instrument channels and the forward water-feeding channel are disposed on a distal end surface of a distal end portion.
Furthermore, an endoscope is used to observe inside of a body cavity where little natural light enters. Therefore, in an endoscope, illumination light introduced through a light guide or the like is irradiated into the body cavity from an illumination window, in order to obtain photographing light to be taken from the observation window.
The endoscope including a bending portion has a plurality of bending pieces in the bending portion, and four bending operation wires for performing a bending operation by pulling and relaxing these bending pieces. Distal end parts of the four bending operation wires are held and fixed by four fixing members to be extended to a proximal end side in a distal end portion of the endoscope, and further inserted and held by four wire guards provided to each of the bending pieces in the bending portion.
Each of these fixing members and wire guards are projected in inner diameter directions of the distal end portion and the bending portion, respectively, and disposed in up, down, left, and right directions of the distal end portion and bending pieces so as to correspond to bending up, down, left, and right directions of the bending portion.
Incidentally, as described above, endoscopes are set to have large observation windows in order to obtain sufficient amount of photographing light by illumination light from illumination windows inside the body cavity where little natural light enters. That is, in accordance with this, it is desirable that endoscopes can perform a good observation by increasing lens diameters of objective optical systems.
Furthermore, if the mucous membrane, blood, filth, or the like in a body cavity adheres on the outer surface of the illumination window, the amount of photographing light to be taken in decreases, so that there is a case where observation performance of each of the image pickup units can not be sufficiently exhibited. Therefore, it is necessary to surely clean also the outer surface of the illumination window.